Ultrananocrystalline diamond cantilever wide dynamic range acceleration/vibration/pressure sensor

ABSTRACT

An ultrananocrystalline diamond (UNCD) element formed in a cantilever configuration is used in a highly sensitive, ultra-small sensor for measuring acceleration, shock, vibration and static pressure over a wide dynamic range. The cantilever UNCD element may be used in combination with a single anode, with measurements made either optically or by capacitance. In another embodiment, the cantilever UNCD element is disposed between two anodes, with DC voltages applied to the two anodes. With a small AC modulated voltage applied to the UNCD cantilever element and because of the symmetry of the applied voltage and the anode-cathode gap distance in the Fowler-Nordheim equation, any change in the anode voltage ratio V 1 /V 2  required to maintain a specified current ratio precisely matches any displacement of the UNCD cantilever element from equilibrium. By measuring changes in the anode voltage ratio required to maintain a specified current ratio, the deflection of the UNCD cantilever can be precisely determined. By appropriately modulating the voltages applied between the UNCD cantilever and the two anodes, or limit electrodes, precise independent measurements of pressure, uniaxial acceleration, vibration and shock can be made. This invention also contemplates a method for fabricating the cantilever UNCD structure for the sensor.

This is a divisional of application Ser. No. 09/543,992 filed Apr. 6,2000 now U.S. Pat. No. 6,422,077.

FIELD OF THE INVENTION

This invention relates generally to ultranocrystalline diamond (UNCD)structures and is more particularly directed to UNCD structures for usein sensors and other devices with special application for highlysensitive, ultra-small devices such as used in micro electro mechanicalsystems.

BACKGROUND OF THE INVENTION

Micro electro mechanical systems (MEMS) cantilever sensors are used asdetectors in shock and acceleration sensors. One common application of aMEMS detector is in the activation of air bags in vehicles. The MEMSdetector is typically made of silicon because of the availability ofsurface micromachining technology. However, these devices have limiteddynamic range because of the limited flexural strength of silicon. Ifthe cantilever deflection exceeds the elastic limit of silicon, thecantilever structure breaks. Moreover, the tribological properties ofsilicon are such that it has a tendency to adhere to surfaces with whichthe cantilever beam comes into contact. In addition, the silicon issubject to high friction and wear in applications involving sliding androlling contact. Because of these characteristics of silicon thesecantilever structures are normally limited to simple on-off switchessuch as in the aforementioned vehicular air bag application, rather thanhaving application to a broad range of measurement devices.

The present invention addresses the aforementioned limitations of theprior art by providing a miniature, highly sensitiveultrananocrystalline diamond structure for use in a sensor having a widedynamic range which is adapted for use in a wide range of applications.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anultrananocrystalline diamond (UNCD) structure for use in sensors andother devices such as in micro electro mechanical systems (MEMS).

It is another object of the present invention to provide an ultra-smallsensor, and a method of fabrication therefor, for precisely measuringacceleration shock, vibration and static pressure over a wide dynamicrange.

A further object of the present invention is to provide a highlysensitive, miniature sensor and associated circuitry which isparticularly adapted for use in atomic force microscopy.

Yet another object of the present invention is to provide a sensorhaving a wide dynamic range which can be used in a wide variety ofapplications such as in, for example, explosive shock sensors,pressure/vibration transducers for aircraft and space vehicles,acceleration sensors/feedback devices for air and ground vehicles, anddata-logging applications.

A still further object of the present invention is to provide a sensorcapable of the simultaneous detection of and discrimination betweenvibration and acceleration.

The present invention contemplates a sensor for measuring anacceleration, vibration or pressure, the sensor comprising a substratehaving a general flat surface; an ultrananocrystalline diamond (UNCD)element having first and second opposed ends, wherein said UNCD elementundergoes deflection from an equilibrium position in response toacceleration, vibration or pressure; a mounting member disposed betweenand coupled to the substrate and the first end of the UNCD element forattaching the UNCD element to the substrate in a cantilever manner,wherein the second opposed end of the UNCD element is deflected from theequilibrium position toward or away from the substrate in response to anacceleration, vibration or pressure; and a detector coupled to the UNCDelement for measuring deflection of the UNCD element from theequilibrium position, wherein the deflection represents an acceleration,vibration or pressure experienced by the UNCD element.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended claims set forth those novel features which characterizethe invention. However, the invention itself, as well as further objectsand advantages thereof, will best be understood by reference to thefollowing detailed description of a preferred embodiment taken inconjunction with the accompanying drawings where like referencecharacters identify like elements throughout the various figures, inwhich:

FIG. 1 is a simplified combined block and schematic diagram of anultrananocrystalline diamond cantilever sensor arrangement in accordancewith one embodiment of the present invention shown in combination withboth an interferometric measurement arrangement and an electricalcircuit measurement arrangement;

FIGS. 2a-2 e illustrate the sequence of steps involved in fabricating afree-standing ultrananocrystalline diamond cantilever sensor arrangementin accordance with one aspect of the present invention;

FIGS. 3a, 3 b and 3 c are electron micrographs of anultrananocrystalline micro electro mechanical system strain gaugefabricated in accordance with the aspect of the present invention shownin FIGS. 2a-2 e;

FIG. 4 is an electron micrograph of a released nanocrystalline diamondcantilever structure for use in a sensor in accordance with the presentinvention;

FIG. 5 is a simplified schematic diagram of a sensor circuitincorporating a nanocrystalline diamond cantilever element in accordancewith the present invention;

FIG. 6 shows graphically the variation of field emission current densitycalculated using the Fowler-Nordheim equation as a function ofdeflection of the nanocrystalline diamond cantilever structure such asin the sensor circuit shown in FIG. 5;

FIG. 7 is another embodiment of a nanocrystalline diamond cantileverstructure in a sensor circuit in accordance with the present inventionincorporating two anodes with each anode disposed on a respective sideof a nanocrystalline diamond cantilever structure;

FIG. 8 is a graphic representation of the variation of total currentcollected by the two anodes in the sensor circuit of FIG. 7 as afunction of the variation in the ratio of separation, or displacement,between the two anodes and the nanocrystalline diamond cantileverelement;

FIG. 9 shows graphically the magnitude of the displacement signal w as afunction of nanocrystalline diamond cantilever element displacement fromthe equilibrium position; and

FIG. 10 is a simplified schematic diagram of another embodiment of ananocrystalline diamond cantilever sensor arrangement in accordance withthe present invention incorporating a flexible membrane which isparticularly adapted for pressure and shock wave measurements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Diamond is a superhard material of high mechanical strength and thermalstability. Table I presents a comparison of selected properties ofsilicon and diamond. From Table I, it can be calculated that theprojected wear life of diamond micro electro mechanical systems-movingmechanical assemblies (MEMS-MMAs) is on the order of 10,000 timesgreater than that of silicon. Studies of the tribo-oxidative propertiesof diamond indicate that diamond may perform significantly better thansilicon and SiC in applications involving sliding/rolling contact inoxygen-containing atmospheres at temperatures up to 950° C. However, asthe hardest known material, diamond is notoriously difficult tofabricate. Thin film methods offer a logical approach to the fabricationof ultra-small diamond structures, but conventional chemical vapordeposition (CVD) methods produce diamond films having large grain size,high internal stress, poor intergranular adhesion, and very roughsurfaces. As a result. conventionally produced diamond films areunsuited for MEMS applications.

TABLE I Property Silicon Diamond Lattice Constant (Å) 5.43 3.57 CohesiveEnergy (eV) 4.64 7.36 Young's Modulus (Gpa) 130 1200 Sheer Modulus (Gpa)80 577 Hardness, Hv (kg/mm2) 1000 10,000 Fracture Toughness 1 5.3Flexural Strength (Mpa) 127.6 2944

The present invention employs phase-pure ultrananocrystalline diamond(UNCD) having morphological and mechanical properties that are ideallysuited for MEMS applications. In particular, recent morphologicalstudies and pseudopotential calculations indicate that UNCD has aflexural strength equal to that of single crystal diamond, and a brittlefracture toughness considerably higher than that of conventionally growndiamond films, and may even exceed the fracture toughness of singlecrystal diamond. UNCD is characterized as having much smaller grain sizethan conventional nanocrystalline diamond (NCD) structures, with onlydiamond and no voids or non-diamond components between grains. Inaddition, UNCD is free of secondary phases and is defined by sharp grainboundaries giving rise to high fracture strength.

Also as shown in Table I, the flexural strength of diamond is 23 timesgreater than that of silicon, permitting much greater forces to beapplied to the cantilever element without breakage. If the diamondshould contact the substrate to which it is mounted, its low coefficientof static friction ensures that the diamond cantilever element will notstick to the substrate. This permits UNCD cantilever elements to be usedas measuring devices for shock, vibration, pressure and acceleration.

Referring to FIG. 1, there is shown a simplified combined schematic andblock diagram of one embodiment of an UNCD sensor arrangement 10 inaccordance with the present invention. The UNCD sensor 10 includes asilicon substrate 12 to which is attached an UNCD cantilever element 16by means of an insulating layer 14. With the UNCD cantilever element 16and silicon substrate 12 separated by the insulating layer 14, thecapacitance between the UNCD cantilever element and silicon substrate isa function of the average distance between the cantilever element andthe substrate. The UNCD cantilever element 16 is in the form of anelongated, linear structure securely attached at one end thereof to thesilicon substrate 12 by means of the insulating layer 14. Insulatinglayer 14 is preferably comprised of a thermally oxidized silicon wafer.In response to an acceleration, vibration or the application of apressure or shock wave, the free end 16 a of the UNCD cantilever element16 is displaced toward the silicon substrate 12. D is the distance fromthe substrate. The free end of the UNCD cantilever element 16 may alsobe displaced away from the silicon substrate 12, although this is notshown in the figure for simplicity.

As shown in FIG. 1, connected between the silicon substrate 12 and theUNCD cantilever element 16 is an electrical detector circuit 34.Electrical detector circuit 34 includes an alternating current I voltagesource 36 and an ammeter 38. Ammeter 38 detects the current I in thecircuit which is given by the following expression:

I=Vωε _(o) A/D  (1)

where V=voltage of the alternating current voltage source;

ω=frequency of the AC voltage;

ε_(o) =dielectric constant of space;

A=the area of the cantilever; and

D=the average distance between the UNCD cantilever element and thesilicon substrate.

Also shown in FIG. 1 is an optical detector arrangement including aninterferometer 20 for measuring the deflection of the free end 16 a ofUNCD cantilever element 16. Interferometer 20 includes a light source22, a beam splitter/compensator 26, and a fixed reflector 24. As thefree end 16 a of the UNCD cantilever element 16 is deflected in responseto an acceleration, vibration or a pressure or shock wave, the phase ofa light beam directed onto the UNCD cantilever element changes and ismeasured by a detector 28 which compares the phase of the light beamoutput by the light source 22 with the phase of the light beam reflectedfrom the UNCD cantilever element.

UNCD is an excellent cold cathode electron emitter with a thresholdfield of 2-5 volts/micron. It is therefore possible to provide a biasvoltage between the UNCD cantilever element and an anode in closeproximity (10-100 μm) in order to measure the emission current. The UNCDelectron emission current is given by the Fowler-Nordheim equation asfollows:

J=A(V/D)² exp(−BD/V)  (2)

where J=current density in amps/cm²;

A and B properties of the cold cathode material;

V=applied voltage; and

D=distance between the silicon substrate (anode) and the UNCD cantileverelement (cathode).

Because the quantity D appears in the exponent of the Fowler-Nordheimequation, the emission current J is extremely sensitive to the gapbetween the silicon substrate and the UNCD cantilever element.

Referring to FIGS. 2a-2 e, there is shown a series of steps involved infabricating a UNCD cantilever sensor in accordance with another aspectof the present invention. In order to fabricate the UNCD cantileverstructure, it is necessary to deposit the UNCD film on a sacrificialrelease layer such as of SiO₂. Using conventional diamond film growthmethods, this is very difficult because the nucleation density is 6orders of magnitude smaller on SiO₂ than on Si. However, the carbondimer growth species in the UNCD process can insert directly into eitherthe Si or SiO₂ surface. In addition, the lack of atomic hydrogen in theUNCD cantilever element fabrication process permits both a highernucleation density and a higher renucleation rate than the conventionalH₂—CH₄ plasma chemistry, and it is therefore possible to grow UNCDdirectly on SiO₂.

The process for fabrication of an UNCD cantilever structure inaccordance with this aspect of the present invention is initiated asshown in FIG. 2a by forming a sacrificial layer 46 of thermally grownSiO₂ on a silicon substrate layer 44. An UNCD layer 48 is then depositedonto the 1 μm thick thermal oxide SiO₂ release layer 46. PECVD (PlasmaEnhanced Chemical Vapor Deposition) is then used to form a SiO₂ hardmask layer 50 on the thin film UNCD layer 48. Photoresist is thendeposited on the SiO₂ hard mask layer 50 and is formed by means ofphotolithography in plural, spaced photoresist deposits 52 a, 52 b and52 c on the SiO₂ hard mask layer 50 as shown in FIG. 2b. The SiO₂ hardmask layer 50 is then also formed in a pattern by means of fluorine dryetching so as to form plural spaced hard mask layer deposits 50 a, 50 band 50 c, disposed between the UNCD layer 48 and the photoresistdeposits 52 a, 52 b and 52 c respectively, as shown in FIG. 2c. Thephotoresist deposits 52 a. 52 b and 52 c are removed and the UNCD layer48 is etched between the hard mask layer deposits 50 a, 50 b and 50 c bymeans of an oxygen plasma as shown in FIG. 2d. This forms plural, spacedUNCD deposits 48 a, 48 b and 48 c. The hard mask layer deposits 50 a, 50b and 50 c and the sacrificial SiO₂ layer 48 are then removed by etchingin HF, leaving cantilever UNCD structures in the form of spaced UNCDdeposits 48 a, 48 b and 48 c.

FIGS. 3a, 3 ba and 3 c are photographs of another configuration of UNCDcantilever structures fabricated by the process shown in FIGS. 2a-2 e.FIG. 3a shows two diamond cantilever structures deposited on a SiO₂release layer which are arranged in facing relation on the releaselayer. The cantilever structures include a series of apertures to allowthe HF etchant access to the sacrificial SiO₂ layer in order to free thecantilever elements from the substrate. The four large comer pads shownin FIG. 3a do not have these apertures and, because of their relativelylarge size, they remain attached to the substrate, with an undercut ofapproximately 7 μm.

Differential motion of the four pads at the corners of the device asshown in FIG. 3a is amplified by the offset support points along thearms of the cantilever elements, permitting the device to function as aMEMS strain gauge. FIGS. 3b and 3 c show increasingly magnified views ofthe free end of the UNCD cantilever structures. The UNCD cantileverstructures on the crossbar represent the scale of a vernier readout fora precise measurement of very small differential motion. Previousattempts at producing such diamond structures were limited by theattainable resolution, which was limited by the diamond grain size(typically≈1 μm). However, the feature size of the vernier scale in thefigures is ≈100 nm.

An UNCD cantilever structure 58 formed as shown in FIGS. 2a-2 e and asdescribed above is shown in the photograph of FIG. 4. Unlikeconventionally grown diamond, which is under considerable compressivestress and curls significantly, often into a tight spiral, when releasedfrom the substrate, UNCD thin films exhibit little interfacial stress.The released UNCD cantilever structure is therefore essentially straightas shown in FIG. 4. This lack of curl in the UNCD cantilever structure58 suggests that the stress is accommodated by Type III (grain boundary)strain. The fabrication of the released UNCD cantilever structure 58shown in FIG. 4 demonstrates that it is possible to produce stable2-dimensional, free-standing UNCD structures using modified Sifabrication technologies. The released UNCD cantilever structure 58exhibits excellent lateral stability and almost no vertical displacementresulting from interfacial stress.

Referring to FIG. 5, there is shown in simplified schematic diagram formanother embodiment of an UNCD sensor arrangement 64 in accordance withthe present invention. As in the previously described embodiment, UNCDsensor arrangement 64 includes an UNCD cantilever element 66 connectedin circuit to a limit electrode 68 by means of a voltage source 70 andan ammeter 72. In the embodiment shown in FIG. 5, voltage source 70 isin the form of a DC voltage source such as a battery. FIG. 6 is agraphic representation of the calculated field emission current densityJ₁ as a function of the separation between UNCD cantilever element 66and limit electrode 68. The field emission current density calculationshown graphically in FIG. 6 is based upon a Fowler-Nordheim analysis ofmeasured UNCD data.

Referring to FIG. 7, there is shown in simplified schematic diagram formstill another embodiment of an UNCD sensor arrangement 76 in accordancewith the principles of the present invention. UNCD sensor arrangement 76includes an UNCD cantilever element 78 having a fixed, stationary end 78a and a free end 78 b. The fixed end 78 a of the UNCD cantilever element78 is attached to a support structure, such as a substrate as previouslydescribed, while the free end 78 b is movable between first and secondlimit electrodes 80 and 82. By using two electrodes, in this caseanodes, on either side of the UNCD cantilever element 78, the UNCDsensor arrangement 76 is capable of simultaneously measuring uniformacceleration, shock, and vibration, and with a slight modification,static pressure and atmospheric shock. A first DC voltage source 86 isconnected between the first limit electrode 80 and the UNCD cantileverelement 78. A second DC voltage source 88 is connected between thesecond limit electrode 82 and the UNCD cantilever element 78. The firstDC voltage source 86 applies a voltage V1 between the first limitelectrode 80 and the UNCD cantilever element 78, while the second DCvoltage source 88 applies a voltage of V2 between the second limitelectrode 82 and the UNCD cantilever element. First and second ammeters92 and 94 measure the current respectively between the first limitelectrode 80 and the UNCD cantilever element 78 and between the secondlimit electrode 82 and the UNCD cantilever element. The spacing betweenthe UNCD cantilever element 78 and the first limit electrode 80 is givenas D1, while the spacing between the UNCD cantilever element and thesecond limit electrode 82 is given as D2. The quantity D1+D2 is fixed. Asmall AC modulation at a frequency ω is applied to the UNCD cantileverelement 78 by means of an AC voltage source 90. The currents J₁ and J₂in the first and second circuits respectively including the first andsecond limit electrodes 80, 82 are respectively given as:

J ₁ =A(V ₁ /D ₁)² exp(−BD ₁ /V ₁)  (3)

J ₂ =A(V ₂ /D ₂)² exp(−BD ₂ /V ₂)  (4)

The parameters A and B have been measured for UNCD films. The totalcurrent collected by the first and second limit electrodes 80, 82 isshown graphically in FIG. 8 as a function of the ratio of D1/D2. Asshown in FIG. 8, there is a wide dynamic range of both the inputdisplacement D1/D2 and the measured current (J1+J2). Because of thesymmetry of the applied voltage and the anode-cathode gap in theFowler-Nordheim equation, there is a change in the anode voltage ratioV1/V2 that exactly matches any displacement of the UNCD cantileverelement 78 from equilibrium. If the V1/V2 ratio is tuned so that theelectron emission currents to the two limit electrodes 80, 82 are equalwhen the UNCD cantilever element 78 is at its equilibrium position, anda small modulation signal having a frequency ω is applied to the UNCDcantilever element the total current (J1+J2) will be modulated at afrequency 2ω as shown in FIG. 8. A static displacement of the UNCDcantilever element 78 from the equilibrium position will result in anoutput current with a frequency ω. The phase of this signal will changeby 180°, depending on the direction of displacement of the free end 78 bof the UNCD cantilever element 78. The amplitude of the ω signal as afunction of UNCD cantilever element displacement is shown graphically inFIG. 9. The 2ω signals and both phases of the ω signals can beindependently detected using lock-in techniques.

If the UNCD sensor arrangement 76 shown in FIG. 7 is subjected tosymmetric time-dependent displacement, i.e., vibration, then all threesignals, i.e., the 2ω signal and both phases of the ω signal, will bedetected simultaneously and the amplitudes of the ω and −ω signals willbe equal. If there is a component of unidirectional acceleration, thenthe ω and −ω signals will be unequal and the difference between them isa measure of the acceleration. The sensitivity for small staticdisplacements can be improved further by using a feedback loop to adjustthe V1/V2 ratio to equalize the ω signals (and maximize the 2ω signal).The change in DC voltage ratio (V1/V2) required to restore theequilibrium condition (amplitude of +ω and −ω signals equal) can berelated to the static displacement via the Fowler-Nordheim equation.

If the UNCD device is subjected to a shock wave, then there will be aninitial displacement in one direction, followed by a damped oscillation.Time-stamped sample and hold circuitry for measurement of the threesignals can be used to determine the duration and intensity of the shockwave. Finally, by allowing one of the anodes, e.g., the one at potentialV1, to be positioned on a movable diaphragm, the device can be madesensitive to atmospheric pressure variations which will change D1, butnot D2. A device in accordance with this aspect of the present inventionfor measuring atmospheric pressure variations is shown in simplifiedschematic diagram form in FIG. 10. The UNCD pressure/shock wave sensorarrangement 104 shown in FIG. 10 includes an UNCD cantilever element 106disposed between a first flexible membrane electrode 108 and a secondlimit electrode 110. As in the previously described embodiment, the UNCDpressure/shock wave sensor arrangement 104 further includes first andsecond DC voltage sources 112 and 114 and first and second ammeters 118and 120. An AC voltage source 116 is connected to the UNCD cantileverelement 106. The small size and high component stiffness of the UNCDpressure/shock wave sensor arrangement 104 provides extremely good highfrequency response and good time resolution.

As shown in FIG. 7, the free end 78 b of the UNCD cantilever element 78may be formed with symmetric diamond tips 84 a and 84 b disposed infacing relation to the first and second limit electrodes 80, 82,respectively. The diamond tips 84 a and 84 b terminate in a very smallradius of curvature, resulting in an enhancement of the electric fieldand a consequent reduction in the required values of V₁ and V₂. Theelectrode spacings D₁ and D₂ are measured from the end of the diamondtip to the respective anode.

In another application, the lower tip in FIG. 7 can be used as the probeof a scanning atomic force microscope (AFM). In this application, thelower electrode is replaced by the sample to be characterized, and thelower tip is brought into contact with the sample, and the V₂ powersupply 88 is not used. The V₁ power supply 86, the cantilever element 78and the up per electrode 80 form a single-sided field emission positionsensor as shown in FIG. 5. The free end of the upper side of thecantilever element 78 may be flat as shown in FIG. 5, or formed with asharp tip as shown in FIG. 7. This design permits the fabrication of anAFM as a single, compact, pre-aligned structure.

There has thus been shown an ultrananocrystalline diamond (UNCD)cantilever wide dynamic range acceleration/vibration/pressure sensor,and method of fabrication therefore, which can also be used as aprecise, alignment-free readout of the cantilever deflection in atomicforce microscopes. Cantilever deflection, and thus the extent ofvibration, acceleration, and pressure, can be detected using eithercapacitative, interferometric or electron emission methods. Using thelatter readout method, the entire UNCD cantilever structure and readoutmechanism can be fabricated as a single, compact, pre-aligned structurecapable of undergoing large displacements without breaking thecantilever element. The sensor is highly sensitive over a wide dynamicsrange and is very small and compact in size making the sensorparticularly adapted for use in micro electro mechanical systems (MEMS)and other devices.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the relevant artthat changes and modifications may be made without departing from theinvention in its broader aspects. Therefore, the aim in the appendedclaims is to cover all such changes and modifications as fall within thetrue spirit and scope of the invention. The matter set forth in theforegoing description in accompanying drawings is offered by way ofillustration only and not as a limitation. The actual scope of theinvention is intended to be defined in the following claims when viewedin their proper perspective based on the prior art.

What is claimed is:
 1. A method for fabricating an ultrananocrystallinediamond (UNCD) cantilever element on a substrate, said method comprisingthe steps of: depositing a sacrificial release layer on the substrate;depositing an UNCD layer on said sacrificial release layer; depositing ahard mask layer on said UNCD layer; depositing photoresist on said hardmask layer and forming said photoresist in discrete, spaced deposits byphotoetching; removing portions of said hard mask layer not disposedbeneath said discrete, spaced deposits of photoresist so as to formdiscrete, spaced deposits of said hard mask layer; removing saiddiscrete, spaced deposits of photoresist and portions of said UNCD layernot disposed beneath said discrete, spaced deposits of said hard masklayer so as to form discrete, spaced UNCD elements disposed on saidsacrificial release layer; removing the discrete, spaced deposits ofsaid hard mask layer disposed on respective discrete, spaced UNCDelements; and removing the sacrificial release layer disposed on thesubstrate for forming each of said discrete, spaced UNCD elements into acantilever structure.
 2. The method of claim 1 wherein said sacrificiallayer is a layer of SiO₂ thermally grown on the substrate.
 3. The methodof claim 2 wherein the step of depositing a hard mask layer includesdepositing a layer of SiO₂ by means of plasma enhanced chemical vapordeposition on said UNCD layer.
 4. The method of claim 3 wherein the stepof forming said photoresist in discrete, spaced deposits includesphotolithographic patterning.
 5. The method of claim 4 wherein the stepof removing portions of said hard masked layer not disposed beneath saiddeposits of photoresist includes reactive ion dry etching.
 6. The methodof claim 5 wherein the step of removing said deposits of photoresistsand portions of said UNCD layer not disposed beneath deposits of saidhard mask layer includes plasma etching.
 7. The method of claim 6wherein the steps of removing the deposits of said hard mask layer andsaid sacrificial release layer includes HF etching.